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Potassium hydroxide

From Academic Kids

</table> The chemical compoundpotassium hydroxide, (KOH) sometimes known as caustic potash, potassa, potash lye, and potassium hydrate, is a metallic base. It is a very alkaline compound used in agriculture to correct the pH of acidic soils. It can also be used as a fungicide or even an herbicide.

Uses

It is a major industrial chemical used as a base in a wide variety of chemical processes.

It is used as a catalyst in reactions like the production of biodiesel, the advantage of using KOH and not NaOH is that NaOH "clumps" and KOH does not.

Some uses of KOH include acrylate ester copolymer coating, defoaming agents used in the manufacture of paper, formulation aid for food, pH control agent, polyethylene resins, textile processing.

Other uses include in veterinary medicine in disbudding calves horns and to dissolve scales and hair; manufacture of cleansers; in wart removal and as a cuticle solvent. This type of compound is also used in washing powders, some denture cleaners, non-phosphate detergents, and drain or pipe cleaners.

It is also a traditional ingredient in the making of soap, and for this purpose was historically obtained in an impure form by steeping wood ash in water for a long period.

Historically, to create potash, one first created potash lye in solution, then one boiled off the remaining liquid.

To create potash lye, one takes an open-bottomed barrel, and places it on a stone base with a groove cut into it, which will direct the resulting liquid into another container. Then one places a layer of straw at the bottom, covered by a layer of sticks. This filter layer will prevent the ashes from contaminating one's solution. Then one fills the barrel with wood-ashes and pours water over it. The water will leach out the potash lye into one's receptacle.

This product will be of variable quality. Historically, it was measured by seeing how high an egg would float in the solution.

To create pearlash, one bakes the potash lye in a kiln until all of the carbon impurities are baked off.

Food preparation

Food uses of lye include washing or chemical peeling of fruits and vegetables, chocolate and cocoa processing, caramel color production, poultry scalding, soft drink processing, and thickening ice cream. Olives are often soaked in lye to soften them, while pretzels and German lye rolls are glazed with a lye solution before baking to make them crisp.

Lye is used to make the Scandinavian delicacy known as Lutefisk (from lutfisk, which directly translated to English means "lye fish"; basically cod jellied in lye). Hominy is dried maize (corn) kernels reconstituted by soaking in lye-water.

de:Kaliumhydroxid fr:Hydroxyde de potassium ja:水酸化カリウム

pl:Wodorotlenek potasu

Properties

General

Name Potassium hydroxide
Chemical formula KOH
Appearance White solid

Physical

Formula weight 56.1 amu
Melting point 679 K (406 °C)
Boiling point 1593 K (1320 °C)
Density 2.0 ×103 kg/m3
Crystal structure ?
Solubility 119 g in 100g water

Thermochemistry

ΔfH0gas -232 kJ/mol
ΔfH0liquid -415.6 kJ/mol
ΔfH0solid -425 kJ/mol
S0solid 79 J/mol·K

Acid - base properties

pKb 0.5 [1] (http://www.chembuddy.com/?left=BATE&right=dissociation_constants)

Safety

Ingestion Very dangerous, may cause permanent GI damage, even death.
Inhalation Very dangerous, high doses may cause serious injury. Long-term hazards also known.
Skin Causes burns, ranging from a rash up to deep ulcers.
Eyes As for skin, may cause irreversible damage.
More info Hazardous Chemical Database (http://ull.chemistry.uakron.edu/erd/chemicals1/7/6956.html)

SI units were used where possible. Unless otherwise stated, standard conditions were used.

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